Light responsive variable resistance control devices for electronic musical instruments



y 1962 J. MARKOWITZ ET AL 3,045,522

LIGHT RESPONSIVE VARIABLE RESISTANCE CONTROL DEVICES FOR ELECTRONIC MUSICAL INSTRUMENTS 4 Sheets-Sheet 1 Filed March 17, 1960 3 5x. BY i TFORNE INVENTORS.

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LIGHT REsRONsIvE VARIABLE RESISTANCE CONTROL DEVICES FOR ELECTRONIC MUSICAL INSTRUMENTS Filed March 17, 1960 4 Sheets-Sheet 2 BY J i Q,

y 4, 1962 J. MARKOWITZ ET AL 3,045,522

LIGHT RESPONSIVE VARIABLE RESISTANCE CONTROL DEVICES FOR ELECTRONIC MUSICAL INSTRUMENTS Filed March 17. 1960 4 Sheets-Sheet 3 F: :3- 4L Z E! 15 b a INVENTORS: 37 \i w Jerome Markowiif; (SN,

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LIGHT RESPONSIVEI VARIABLE RESISTANCE CONTROL DEVICES FOR ELECTRONIC MUSICAL INSTRUMENTS Filed March 17, 1960 4 Sheets-Sheet 4 Ixpress/cn.

Pea a Z fies/37h nce of Ugh? Responsive fies/31hr Ep/cal Curve show/119' leza'l'zlanablfi Aefween Btpreas/on BJaZpoa/Tfon anal hesr's'rarue 9f" 3,045,522 Patented July 24, 1962 3,045,522 LIGHT RESPONSIVE VARIABLE RESISTANCE CONTROL DEVICES FOR ELECTRONIC MUSI- CAL INSTRUMENTS Jerome Markowitz, Allentown, and Milton F. Nelson, Macungie, Pa., assignors to Allen Organ Company, Macungie, Pa., a corporation of Pennsylvania Filed Mar. 17, 1960, Ser. No. 15,592 1 Claim. (Cl. 84-127) This invention relates to control devices for electric or electronic musical instruments, such as electronic organs and the like; and more particularly concerns a unique relay type control device having a noiseless light responsive variable action, which device can be used, for example, to control the sound expression of such instruments by turning on or off the musical sound or audio effects produced thereby, at various tone or intensity levels, in such manner as to eifect new and highly desirable results.

It is more or less generally apparent to those active in the electronic organ field, that the conventional foot pedal and otherwise operated electric relays of modern electronic organs, when used for closing or opening audio circuits, produce a combination clicking sound and unnaturally abrupt on or off noise or sound effect. Such sound effects are detrimental to the rendition of organ music in that they are annoying or otherwise disturbing, particularly to the listeners whose sense of hearing is highly sensitive, or acute, or to those more conscious of fine tone quality, purity, or perfection. In some instances, variable capacitors are utilized in such electronic organs as a means of tonal expression control. However, such capacitors can only be utilized in combination with specially designed circuits, the installation of which, in certain type electronic organs, is either not feasible or presents practical problems that cannot be readily solved. In most of the modern electronic organs, potentiometer type devices are utilized for controlling or varying the sound volume or expression. The application or utilization principle of potentiometer control devices for this purpose is practically the same as it is in a radio apparatus. Nevertheless, in an electronic organ, such control devices are usually of the foot operated type and are consequently subject to very extensive and more or less rough usage as well as rapid wear, which sooner or later causes improper functioning thereof. In other words, the presently available control devices of the type indicated are practically or commercially unsatisfactory for one reason or another. Furthermore, such devices do not meet certain special demands and requirements of modern electronic organ design and engineering practice. Such, for example, as noiseless and flawless functioning during an estimated period of time which may involve perhaps millions of cycles of operation. In this connection it may be of interest to note that, after a diligent search of the market during the past several years for a noiseless and otherwise satisfactory audio control device of the type here involved, none could be found which the manufacturers thereof were willing to supply under a guarantee that its performance, capability and lasting quality would meet the indicated special demands and requirements.

One object of our invention is to provide a novel control device for electronic musical instruments and the like, which successfully overcomes the indicated detrimental and unsatisfactory aspects and phases of the similar prior art devices and which also meets the special demands and requirements of modern electronic organ design and engineering practice.

Another object is to provide such a control device having certain structural and functional features of advantage over the similar devices of the prior art.

A further object is to provide such a control device which has a variable light responsive action that is noiseless and practically never wears out.

An additional object is to provide such a control device which can be readily cooperatively combined with any electronic organ or the like and one which does not require any special form of electric circuitry or any special adjustment in connection with its use or operation.

Another object is to provide such a control device having a Variable light responsive action that can be directly or remotely effected.

Another feature of our invention resides in the provision of such a control device which, in one of its forms, is adapted for use as a gradual on or off relay, that is capable of being actuated by a stop key of an electronic organ, or by some other actuator of the organ control system.

It is also an object to provide a novel foot operated pedal structure or unit having our unique control device embodied therein for actuation thereby.

Another object is to provide such a control device which comprises a structure having a chamber, a light source unit for effecting a light beam, a light responsive variable resistance element, means mounting said unit and element Within the chamber in relatively spaced cooperatively aligned relationship so that the element is subjectable to the light beam, and means for controlling the extent of the light beam subjection of the element.

A further object is to provide such a control device in which the said structure includes one or more additional features, such as a member arranged to extend crosswise of the chamber and having a cross-sectional pattern establishing aperture or passage for the light beam, light diffusing means within the chamber arranged in spanning relation with said aperture, a shutter-like light beam intercepting or obstructing member that is reciprocatively operable transversely of the path of travel of the light beam, and a pedal or other element for effecting actuation of said shutter-like member.

It is also an object to provide a novel electronic musical instrument, such as an electronic organ, which embodies the said control device in a new manner so as to effect highly desirable results.

With these and other objects in view, which will become more readily apparent from the following detailed description of the various practical and illustrative embodiments of our improvements shown in the accompanying drawings, our invention comprises the novel control device, electronic musical instrument elements, features of construction and arrangement of parts in cooperative relationship, as more particularly indicated and defined by the hereto appended claim.

In the drawings:

FIGURE 1 is a wiring diagram that depicts a portion of the circuitry of an electric or electronic organ system which exemplifies one practical form of musical instrument and one form of control device in accordance with our invention.

FIG. 1 is a sectional view of the on-olf relay form of our light responsive resistor control device.

FIG. 2 is a top view of one form of control device structure, or foot pedal unit, that forms part of our invention.

FIG. 3 is a side elevational view of the unit shown in FIG. 2, with certain parts thereof broken away so as to disclose various structural details.

FIG. 4 is an enlarged elevational view of .the control device unit shown in FIGS. 2 and 3, as seen by looking at the latter from the right.

FIG. 5 is a cross-sectional view of the chamber forming structure and certain other elements of the control device, taken substantially as indicated by the arrows 5-5 on FIG. 4.

FIG. 6 is an elevational sectional view, on a reduced scale, taken substantially as indicated by the arrows 66 on FIG. 4, but with the pedal and a certain aperture indicated in dot-and-dash outline for clarification purposes.

FIG. 7 is an elevational view, similar to FIG. 6, but showing certain parts of the latter in another position.

FIGS. 8 and 9 are, respectively, a side elevational view and an edge view of a light diffusion element, or plate, which forms part of the control device of our invention.

FIG. is a detail side elevational view of a flat element, or plate, having a light beam passage forming aperture of a certain configuration, which plate forms a part of the control device of our invention, and

FIG. 11 is a typical curve chart showing the relationship between the foot pedal operated shutter element of the unit shown in FIGS. 2, 3 and 4, and the resistance value of the light responsive resistor element of said unit.

In the drawings, one form of foot pedal control device, in accordance with our invention, is disclosed by FIGS. 2 to 10 inclusive; FIG. 1 discloses a relay type control device which forms part of our invention; and FIG. 1 is a schematic representation of an electronic organ system in accordance with our invention having embodied therein the said control devices in a manner that exemplifies their practical use and application.

For purposes of exemplification, or illustration, only those parts of an electronic organ system are indicated in FIG. 1, as will facilitate an understanding of the application and operation of the novel improvements, the performance of their intended function and the manner in which the said improvements achieve certain unique and desirable benefits, results and advantages. Therefore, it is to be understood that the electronic organ system partly disclosed in FIG. 1, is representative of a complete system which includes, in cooperative combination with the various indicated organ system parts and elements of our invention there indicated, all those other usual standard or conventional parts of a modern electronic organ system that make the same complete and operative in every respect in the usual and well known manner of the modern electronic organ practice. From this disclosure it will be readily apparent to those skilled in this art how our improvements can be utilized to accomplish substantially the same results, benefits and advantages with other types of electric or electronic musical instruments.

It will facilitate an understanding of our invention to first consider the construction and operation of our novel control devices so that the various features thereof may be kept in mind when subsequently reading the description of the electronic organ system in which said devices are embodied.

Accordingly, it is noted that the foot pedal control device of FIGS. 2-10 generally comprises a unitary frame structure 1, on which is pivotally supported a foot treadle or pedal 2, and a housing structure 3, having a substantially light-proof chamber 4, that has mounted therein certain light responsive control means hereinafter described.

The frame structure 1 is adapted to be supported or secured in position at the console of the organ at a location that enables convenient foot operation of the pedal 2 by the organist.

The foot pedal 2 is of the usual type commonly associated with pipe organs and electronic organs for the purpose of enabling foot operation of the expression control means, or variable loudness means, of the entire organ system, or of a certain section thereof, or of a particular unit thereof.

As more particularly indicated in FIG. 3, the pedal 2 is pivotally mounted on the frame structure 1, so as to be movable between its full line position and the dotand-dash line position thereof. The pivotal connection of the foot pedal 2 and frame structure 1 comprises a metal hinge or strap, the upper hinge wing H of which is welded or other-wise secured to a bottom metallic plate,

or part of the foot pedal 2. The circular end portion of the hinge extends in turnable relation about a shaft 5 that is fixedly secured to a member 1 of the frame structure 1 by two screws, one of which is indicated at 6 in FIG. 3, which screws extend vertically through apertures provided therefor in the end sections of the shaft 5 and are anchored in the frame member 1 In order to enable smooth tilting or turning movement of the pedal 2, about the shaft 5, and to effect properly adjusted frictional engagement of the circular portion of the hinge with the shaft 5, the lower wing section H of the hinge is arranged to be adjustably movable toward and from the upper fixed hinge wing section by a pair of screws, one of which is indicated at 7 in FIG. 3.

At the lower end of the frame structure 1 there is provided a horizontally extending frame member 1*, to which is fixedly secured a resilient cushioning element 8, that is contacted by the lower end of the pedal 2 so as to stop its movement when the latter is moved to its dot-and-dash line position as shown in FIG. 3. The element 8 may be made of felt, rubber, or some other resilient material suitable for effecting soft and noiseless stopping of the pedal movement in one direction. To effect similar stopping of the pedal movement in the opposite direction two similar cushioning elements 9 and 9 are fixedly secured to the top surface of the housing structure 3, as clearly indicated in FIGS. 3 and 4.

Rigidly secured to the underside of the pedal 2, at the upper end thereof, is an angular bracket 14), to which is fixedly attached, by two screws or bolts 11 and 12, a flat plate 13, of aluminum or the like. The plate 13 is provided with an extension 13 of such shape and size as to serve the purpose of a light beam intercepting shutter in cooperation with the lightproof chamber 4, in a manner hereinafter more fully explained. In order that the shutter extension 13 may be precisely moved in a vertical plane, up and down, during the action of the pedal 2, certain means are provided which accomplish this in conjunction with an arrangement that enables adjustably controlled softness of the pedal movement and firm holding action thereof in the selected positions to which the pedal is moved by the operator thereof. The said means generally comprises a flat bifurcated member 14, that is pivotally suspended from the screw bolt 12, a bracket 15 that is secured to the housing structure 3 by two screws 16 and 17, a stud shaft 18 that is fixedly secured to the bracket 15, a spiral compression spring 19 that is mounted on the stud shaft 18 between two washers 20 and 21, a spring pressure adjusting nut 22 mounted on the screw threaded outer end of the stud shaft 18, and a pair of friction discs or Washers 23 and 24, that exert a frictional pressure action on both sides of the bifurcated member 14. By adjustably turning the nut 22, the pressure of the spring 19 can be increased or decreased, as desired, so as to correspondingly vary the frictional contact pressure between the washers 23 and 24 and the opposite surfaces of the bifurcated portions of the member 14. The washers 23 and 24 may be made of a suitable material, such as a plastic, fibrous or rubber material, which provides the desired degree of contact friction and sliding action between the washers and member 14, when the latter is moved up and down therebetween during the operating action of the pedal 2.

The housing structure 3 generally comprises two similar housing sections 3 and 3 each of which has a cylindrical chamber forming aperture extending lengthwise therethrough in such manner that both said apertures combinedly form the continuous lightproof chamber indicated by the numeral 4. The housing sections 3 and 3 are made of a dielectric material, such as wood, plastic material, etc., and are alignedly secured to a dielectric base plate 25, by screws 26, which base plate is in turn secured to horizontally extending projections 1 of the frame structure 1 by screws 27.

As best seen in FIGS. 4 and 5, the housing sections 3 and 3 are mounted in axially aligned but centrally separated relation with each other so as to provide an intermediate area or spacing arrangement therebetween for the accommodation, in adjacent or grouped relation, of the shutter element 13 a pair of similar felt separators 28, 29, an opaque plate 30 of metallic or fibrous material that is provided With an aperture 30 of a certain size and configuration as shown in FIG. 10, and a light diffusion plate or element 31. The felt separator 29 is attached by a suitable adhesive to the inner edge of the housing member 3'. The felt separator 29, plate 30 and light diffusion element 31 are also attached to each other and to the inner edge of the housing member 3 by a suitable adhesive.

The housing member 3 is closed at its outer end by a dielectric end Wall forming member 32 that is secured in position by screws, one of which is indicated at '33. The housing member 3- is closed at its outer end by a metallic end wall forming member 34 that is secured in position by screws, one of which is indicated at 35.

The end wall forming member 34 is provided with a circular aperture that is located in central relation with the chamber 4 and in said aperture there is detachably mounted a conventional type of lamp socket 36 that in turn separately holds a small electric lamp or bulb 37 adapted to provide a suitable light beam source in the chamber 4. For the purpose of our invention, we have found that a satisfactory light beam can be established by utilizing a standard lamp of the type sold by the General Electric Company and identified as No. 53. Conductors 37 and 37 are arranged to lead to the circuit power source to effect illumination of the light bulb 37.

The end Wall forming member 32 has fixedly secured to the inside thereof, in central relation with the chamber 4, a light responsive resistor element 38 which may be of the standard type made and sold 'by the Ferroxcube Corporation and identified as LDRC7. Conductors 38 and 38 are arranged to lead to the respective circuit locations of connection of the light responusive resistor element 38.,

The light diffusin element 31 consists of a thin sheet of translucent material, such as a high quality tracing paper, plastic material, etc. The said light diffusing element 31 serves to break up the beam of light produced by the filament cluster of the light bulb 37, so that a light area or light beam is directed toward the element 38 which is of uniform intensity and which in shape and size is defined by the opening 30 of the plate 30. We have found in practice that the aperture 30 of the plate 30, when made of a relative shape and size as indicated, will provide a light beam, or a crosssectional light beam area for proper cooperation with the light responsive resistor element 38. When the said light beam or light beam area is increased or diminished by the movement of the shutter element 13 transversely thereacross, as the pedal 2 is moved between its closed position indicated by FIG. 6 and its open position indicated by FIG. 7, there Will be effected a resistance variation in the element 38 that is approximately logarithmic in respect to the displacement of the pedal 2. words, the configuration of the shutter element 13 in conjunction with the shape of the aperture 30 determines the relationship between the light responsive action of the resistor element 38 and the position of the pedal 2, in its path of travel from one of its extreme positions to the other.

The exact shape of the aperture 30*, Which is shown in FIG. as being approximately triangular, is established by plotting a curve which indicates the resistance of the light responsive element 38 and the relative position of the pedal 2. The characteristics of the element 38 and the brillance of the light bulb 37 are also factors affecting the shape of such a curve. FIG. 11 discloses a In other,

typical curve plotted in the manner indicated which was established with a light bulb 37, light responsive element 38 and shutter element 13 arranged and operated substantially as shown and described. In this connection, it will be understood that many variations in the shape of the aperture 30 and the shape of the shutter element 13 can be conceived to establish a resistance versus pedal-position curve similar to that shown in FIG. 11 and indicative of operational results that are satisfactory and desirable in accordance with our invention.

FIG. l shows a cross-sectional view of a certain relay type device in accordance with our invention. This device comprises a lightproof enclosure 40, a light responsive resistor element or cell 41 which is similar to the element 38, and an incandescent bulb or lamp 42, which is similar to the light bulb 37. The elements 41 and 42 are so arranged relative to each other that energization of the light bulb 42, by a suitable power source, Will cause the light rays or light beam thereof to activate the element 41. The light responsive element 41 has a socalled dark resistance which is in excess of several megohms and an illuminated resistance which is determined by the degree of illumination of the sensitive surface of the cell. In the arrangement of FIG. 1 the dark and light resistance values, in effect, substantially represent variations in the light dependent resistance between open and short circuit resistance conditions respectively, and consequently provide a certain relay action when placed in series with a signal circuit as hereinafter illustrated in connection with the description of our improved electronic organ system. Since the incandescent filament of the bulb 42 does not reach full brilliance instantaneously, but requires a finite period of time to do so, the resistance of the light responsive element 41 likewise does not instantaneously change from a maximum to a minimum condition, but rather follows a curve of gradual change between maximum and minimum, depending upon the heating time or incandescence characteristic of the light bulb 42. This relatively gradual change of resistance makes it possible to utilize the device of FIG. 1 in a circuit to effect a desirable gradual and noiseless change from open to closed circuit conditions. Therefore, the utilization of this device in our improved electronic organ system provides the advantage, among others, of eliminating the abrupt square wave characteristic of the type produced by mechanical contact relays that are utilized, as a stop switching arrangement in certain prior art electronic organ systems, which mechanical contact relays produce a distinct click in connection with their operation.

Referring now to FIG. 1 of the drawings, which illustrates the electronic organ system improvements of our invention in a more or less schematic manner, it has been previously pointed out that only those parts are shown in said figure as will make it clear how our improvements are cooperatively incorporated in such a system. To this end, two organ keys 43 and 44 are shown, which keys are of the type present on an organ console for the purpose of actuating the switches that control the tone generating circuitry of the proper frequency for the particular key that is depressed. Tone generators 45 and 46 are indicated which may be of the type known as Hartley oscillators having transistors as the amplifying element, but which may also be of any of the usual or conventional type oscillators that will produce an electrical tone, or signal, of the proper frequency and amplitude when connected to a suitable source of energy in well known manner.

A suitable source of energy is shown at 47, in the form of an electrical battery having one of its terminals grounded and the ungrounded terminal Y thereof arranged to be connected to the various terminals of the system at the points also indicated by the letter Y. It will be understood that the said battery type electrical energy source is shown only for convenience and simplification, and that other appropriate sources of electrical energy can be utilized, such as a rectifier type power unit, 01' any other unit which is adapted to convert electrical power line energy into the electrical energy required to operate the organ system here involved.

The signal outputs of the oscillators 45 and 46 are connected to a common bus or line 48 through resistors 49 and 50 which serve to isolate the individual oscillators 45 and 46 from each other, and also establish a desired voltage level in the common bus 48.

It is to be understood that the two oscillators 45 and 46, are part of a complete set of similar oscillators that are provided to cover a span of frequencies of five octaves or more, depending upon the range of the organ system.

The common oscillator bus 48 connects with three relay devices R R and R of the one-off type shown in FIG. 1 and previously described, which devices are actuated at the organ console by stop tablet type switches S S and S The said stop tablet type switches are of the usual form found on any organ console and provided for the purpose of enabling the organist to select various tone colors by depressing the proper such stop tablet.

When any of the stop switches S S S are actuated, the circuit from the power source 47 to a respective incandescent bulb B B and B of the relay devices R R R is completed, which results in illumination of a respective light responsive element L L L of the relay devices R R R and a closed condition in the selected signal circuit. Since, as previously explained, the incandescent filaments of the bulbs B B B do not reach full brilliance instantaneously, but require a finite period of time to do so, the resistance of the light responsive elements L L L likewise does not instantaneously change from the maximum to the minimum resistance condition, but rather follows a curve of gradual change from maximum to minimum resistance, as determined by the heating time characteristic of the incandescent bulbs B B B that are cooperatively associated with said light responsive elements L L L Resistor and capacitor combinations 50 and 51 are connected between the relay switches R R and an amplifier 52, which combinations serve as filter and/ or attenuator networks and function to modify the character of the signal generated by the oscillators 45 and 46 so as to provide various tonal etfects which are selected by the organist at the console by manipulation of the stop tablets S S and S The amplifier 52 is a conventional audio amplifier which drives a conventional loudspeaker 53, such conventional items being of the type commonly utilized in modern electronic organ systems.

The control device as shown in FIGS. 2-10 is schematically indicated by the numeral 54 in FIG. 1, except that in said figure, two light responsive elements are shown to indicate that such a modification is within the purview of our invention. This device performs the function of a variable type of attenuator which can be continuously varied when connected in shunt with the amplifier input of the organ system of FIG. 1.

A similar or modified form of such an attenuator arrangement is schematically indicated by the numeral 55 in FIG. 1.

Either of the control devices indicated at 54 and 55 may be arranged to function as a continuously variable attenuator in the organ system of FIG. 1, by connecting the terminal X thereof with the conductor that leads to the amplifier 52, in the manner of the device 54 which is shown so connected in FIG. 1.

In the schematic representation, indicated at 54 in FIG. 1, of the control device shown in FIGS. 2-10, certain corresponding parts are numbered as in FIGS. 2-10, such as the foot or expression pedal '2, incandescent lamp or bulb 37 and light responsive resistor element 38. Such parts are also identified by the same reference numerals in the modified form of control device schematically indicated at 55 in FIG. 1. The difference between the control devices, as indicated at 54 and 55 in FIG. 1, resides in the device 55 having the elements 37 and 38 housed together in a lightproof enclosure, similar to that shown at 40 in FIG. 1 A potentiometer 56 is mechanically connected by means of suitable levers and/or gears (not shown) to the expression pedal 2. The potentiometer, when connected to a suitable source of energy, such as the battery 47, will provide a variable source of voltage to the light bulb 37. Movement of the potentiometer armature by means of the pedal 2 will result in control of the lamp brilliancy which in turn determines the resistance of the light responsive resistor element 38. In this form of control device, the shape of the curve of FIG. 11 would be established by plotting the resistance of the element 33 against the position of the expression pedal 2, by providing the potentiometer 56 with a suitable taper such as is commonly available in composition carbon type potentiometers.

Modifications It will be apparent to those skilled in this art that the improvements specifically shown and described, can be changed and modified in various ways without departing from the invention herein disclosed. For example, instead of utilizing a light diffusion element, as indicated at 31 in FIGS. 5, 8 and 9, the incandescent bulb 37 could have an area of opaque paint or the like applied to the front surface thereof, so as to allow only indirect or diffused light rays to be transmitted to the light responsive element 38.

We claim:

A volume control for an electronic musical instrument comprising a source of light, a light responsive element spaced from said source, an opaque screen between said source and said element, said screen having an aperture therein of generally triangular shape and having two of its sides lying in opposed exponential curves, and a movable shuter covering said screen.

References Cited in the file of this patent UNITED STATES PATENTS 1,556,766 Ybarrondo Oct. 13, 1925 2,796,534 Williams June 18, 1957 OTHER REFERENCES Kodak Ektron Detector, published 1955. Photo-Electric Handbook, G.A.G. Ive, published 1955, page 2, 

